1. Field of the Invention
The present invention relates to a stepping motor, and more particularly to a claw-pole permanent magnet stepping motor.
2. Description of the Related Art
A permanent magnet (PM) stepping motor, usually called as PM stepping motor, having super miniaturized claw-poles is widely used in various equipment, such as a driving source for a lens driving of a camera and a feeding or a tilting of an optical media apparatus because it is capable of high precision position control with a comparatively simple structure.
FIG. 1 illustrates a schematic structural diagram of a PM stepping motor having claw-poles according to the conventional art. Referring to FIG. 1, the PM stepping motor is configured such that a rotary shaft 70 is inserted into an inner portion of a housing 10 and rotatably supported by the housing 10, a rotor 40 is press fitted into the rotary shaft 70, and a pair of stators 20 and 30 are disposed along an inner circumferential surface of the housing 10 for being arcuately aligned around the rotor 40.
The stators 20 and 30 axially aligned alonside are comprised of coil bobbins 22 and 32 wound by stator coils 23 and 33 and stator yokes 21 and 31. Each stator yoke 21 and 31 is disposed at one side of the housing 10 for supporting the coil bobbins 22 and 32. Each state yoke 21 and 31 has stator claw-poles 21a and 21b having a plurality of N poles and S poles. The stator claw-poles 21a and 21b are alternately aligned adjacent to each other around the circumference of the coil bobbins 22 and 23 in a comb-like form.
Meanwhile, the rotor 40 has a cylindrical shape which is formed of permanent magnet divided into a plurality of parts in a peripheral direction so as to alternately magnetize the parts into different polarities, and is centrally positioned at the stator yokes 21 and 31 and rotatably press fitted into the rotary shaft 70. The rotary shaft 70 is rotatably supported by a pair of bearings 50 and 60 each disposed at both sides of a central axial hole of the housing 10.
In the conventional claw-pole PM stepping motor thus structured, the stator yokes 21 and 31, the coil bobbins 22 and 32 and the stator coils 23 and 33 are concentrically and radially arranged at the periphery of the rotor 40, such that a problem arises of the outer diameter of the motor tends to be enlargeably formed.